In December 1776, the regiment was assigned to George Washington's main army and was present at Assunpink Creek and fought at Princeton in January 1777.

[1] Richard Humpton, a former captain in the British Army and Seven Years' War veteran, was appointed colonel on 25 October.

The Pennsylvania infantry company organization of October 1775 was weaker than the Continental standard by one lieutenant, the two musicians, and eight privates.

[8] Before the Battle of Princeton on 3 January 1777, the Pennsylvanians made the second-night march in a row with very little sleep, and the soldiers were exhausted.

[9] The order of march for John Sullivan's division was a vanguard under Isaac Sherman followed by the brigades of Arthur St. Clair and Mifflin.

While Sullivan's column swung to the right, the troops under Nathanael Greene turned to the left, led by 350 men under Hugh Mercer.

Mawhood's soldiers advanced toward the Thomas Clark House and hill but were halted by cannon fire from Joseph Moulder's artillery company.

[11] As the British attack stalled, Washington patched together a line from the brigades of John Cadwalader, Daniel Hitchcock, Edward Hand, and Mifflin.

Still, he was later sent on detached duty, and the 1st Pennsylvania Brigade's commander Brigadier General Anthony Wayne led the division in his absence.

Wayne's 2,000-man division deployed in a single battleline 500 yards (457 m) east of Chadds Ford on Brandywine Creek.

At the same time, Howe directed Charles Grey to conduct a silent night bayonet attack on Wayne's Pennsylvanians.

[18] Just after midnight on the 21st, the Battle of Paoli began when an American dragoon alerted the camp, and Wayne ordered his soldiers out of their shelters.

One of the guns broke down, blocking the road, and as the Pennsylvanians waited for the obstruction to be cleared, the British burst through the 1st Regiment and fell on the immobile column with bayonet and sword.

[23] As Sullivan's line passed the Benjamin Chew House, 120 men of the 40th Foot took refuge in the building, but the Americans ignored them and pressed onward into the fog.

Accordingly, two cannons of Proctor's 4th Continental Artillery Regiment and two captured British 6-pound guns began firing at the Chew House.

[25] Completely isolated to the east of Germantown Road and several hundred yards south, Wayne heard the racket, about-faced his division, and started back in the direction of the Chew House.

[27] At the time the regiment went into winter quarters at Valley Forge, Humpton's field officers were Lieutenant Colonel Caleb North and Major Francis Mentges.

On 22 June, Washington ordered each brigade in the army to detach one officer and 25 sharpshooters to join a corps led by Daniel Morgan.

On 24 June, Morgan was directed to annoy the right flank and rear of Sir Henry Clinton's retreating British army.

Washington also sent a 1,500 detachment of picked men from the entire army under Charles Scott to harass the British left flank.

However, the detachments to Lee's advance guard reduced the brigade's numbers to 35 officers, 51 sergeants, and 401 rank and file, or 487 men.

[31] At the beginning of the action, Lee's vanguard sparred with the British rear guard but quickly retreated when Clinton advanced at the head of 6,000 men.

Clinton began a deliberate withdrawal when an American battery on Comb's Hill started to enfilade his lines from the left.